A part of this project focuses on leiomyomata (fibroids) and examines factors related to their pathogenesis, diagnosis and/or potential treatment. We previously investigated the effect of single doses of CDB2914 (ulipristal acetate, UPA) on the menstrual cycle in women, and showed that doses of 100 or 200 mg retard folliculogenesis and precipitate menses, in the follicular and luteal phase respectively. Two randomized double-blind placebo-controlled clinical trials from our group showed reduction in fibroid size in women receiving UPA at a daily dose of 10 or 20 mg for three months, as compared to women receiving placebo. One of these studies showed continued efficacy during a second three-month study. We have also evaluated effects of 5 years of prolonged exposure to UPA in a patient with benign metastasizing leiomyoma did not result in endometrial hyperplasia or neoplasia. Endometrial biopsies were performed at established intervals to monitor for intraepithelial neoplasia or progesterone receptor modulator-associated endometrial changes (PAECs). The patient tolerated UPA therapy well; there was no evidence of hyperplasia or proliferative changes associated with progesterone-associated endometrial changes.